Intravascular stent

ABSTRACT

A stent in a non-expanded state has a first and second expansion column, each consisting of a plurality of expansion strut pairs. An expansion strut pair includes a first expansion strut, a second expansion strut and a joining strut that couples the first and second expansion struts at one end. Expansion strut pairs include expansion strut pair first and second corners formed where the joining strut couples the first and second expansion struts. A connecting strut column, formed of a plurality of connecting struts couples the first and second expansion columns. Connecting struts include a proximal section, a distal section and an intermediate section. The proximal section is coupled to the corner of an expansion strut pair of the first expansion column, and the distal section is coupled to the joining strut of an expansion strut pair of the second expansion column intermediate the expansion strut pair first corner and the expansion strut pair second corner.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of Provisional PatentApplication No. 60/017,484 filed Apr. 26, 1996, the disclosure of whichis incorporated by reference. This application is a continuation in partof U.S. patent application Ser. No. ______, (Attorney Docket No.17828:02), filed Mar. 25, 1997, entitled “Intravascular Stent”, and acontinuation in part of U.S. patent application Ser. No. ______,(Attorney Docket No. 17828.703), filed Mar. 25, 1997, entitled“Intravascular Stent”, and a continuation in part of U.S. patentapplication Ser. No. ______ , (Attorney Docket No. 17828.704), filedMar. 25, 1997, entitled “Intravascular Stent” and is related to U.S.patent application Ser. No. ______, (Attorney Docket No. 18461.709),filed Apr. 25, 1997, entitled “Intravascular Stent” each having samenamed inventor G. David Jang and being incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to intravascular stents, and moreparticularly to an intravascular stent which provides easy introductionthrough tortuous sections of vessels.

[0004] 2. Description of the Related Art

[0005] Angioplasty, either coronary or general vascular, has advanced tobecome the most effective means for revascularization of stenosedvessels. In the early 1980's, angioplasty first became available forclinical practice in the coronary artery, and has since proven aneffective alterative to conventional bypass graft surgery. Ballooncatheter dependent angioplasty has consistently proven to be the mostreliable and practical interventional procedure. Other ancillarytechnologies such as laser based treatment, or directional or rotationalarthrectomy, have proven to be either of limited effectiveness ordependent on balloon angioplasty for completion of the intendedprocedure. Restenosis following balloon-based angioplasty is the mostserious drawback and is especially prevalent in the coronary arterysystem.

[0006] Many regimens have been designed to combat restenosis, withlimited success, including laser based treatment and directional orrotational arthrectomy. Intravascular stenting, however, noticeablyreduces the restenosis rate following angioplasty procedures. Theprocedure for intravascular stent placement typically involvespre-dilation of the target vessel using balloon angioplasty, followed bydeployment of the stent, and expansion of the stent such that thedilated vessel walls are supported from the inside.

[0007] The intravascular stent functions as scaffolding for the lumen ofa vessel. The scaffolding of the vessel walls by the stent serve to: (a)prevent elastic recoil of the dilated vessel wall, (b) eliminateresidual stenosis of the vessel; a common occurrence in balloonangioplasty procedures, (c) maintain the diameter of the stented vesselsegment slightly larger than the native unobstructed vessel segmentsproximal and distal the stented segment and (d) as indicated by thelatest clinical data, lower the restenosis rate. Following anangioplasty procedure, the restenosis rate of stented vessels has provensignificantly lower than for unstented or otherwise treated vessels;treatments include drug therapy and other methods mentioned previously.

[0008] Another benefit of vessel stenting is the potential reduction ofemergency bypass surgery arising from angioplasty procedures. Stentinghas proven to be effective in some cases for treating impending closureof a vessel during angioplasty. Stenting can also control and stabilizean unstable local intimal tear of a vessel caused by normal conductduring an angioplasty procedure. In some cases, an incomplete or lessthan optimal dilatation of a vessel lesion with balloon angioplasty cansuccessfully be opened up with a stent implant.

[0009] Early in its development, the practice of stenting, especially incoronary arteries, had serious anticoagulation problems. However,anticoagulation techniques have since been developed and are becomingsimpler and more effective. Better and easier to use regimens arecontinuously being introduced, including simple outpatientanticoagulation treatments, resulting in reduced hospital stays forstent patients.

[0010] An example of a conventional stent patent is U.S. Pat. No.5,102,417 (hereafter the Palmaz Patent). The stent described in thePalmaz Patent consists of a series of elongated tubular members having aplurality of slots disposed substantially parallel to the longitudinalaxis of the tubular members. The tubular members are connected by atleast one flexible connector member.

[0011] The unexpanded tubular members of the Palmaz Patent are overlyrigid so that practical application is limited to short lengths. Evenwith implementation of the multilink design with flexible connectormembers connecting a series of tubular members, longer stents can notnavigate tortuous blood vessels. Furthermore, the rigidity of theunexpanded stent increases the risk of damaging vessels duringinsertion. Foreshortening of the stent during insertion complicatesaccurate placement of the stent and reduces the area that can be coveredby the expanded stent. There is, further, no method of programming thestent diameter along its longitudinal axis to achieve a tapered expandedstent, and no method of reenforcement of stent ends or other regions isprovided for.

[0012] Another example of a conventional stent patent is WO 96/03092,the Brun patent. The stent described in the Brun patent is formed of atube having a patterned shape, which has first and second meanderpatterns. The even and odd first meander patterns are 180 degrees out ofphase, with the odd patterns occurring between every two even patterns.The second meander patterns run perpendicular to the first meanderpatterns, along the axis of the tube.

[0013] Adjacent first meander patterns are connected by second meanderpatterns to form a generally uniform distributed pattern. Thesymmetrical arrangement with first and second meander patterns havingsharp right angled bends allows for catching and snagging on the vesselwall during delivery. Furthermore, the large convolutions in the secondmeander pattern are not fully straightened out during expansion reducingrigidity and structural strength of the expanded stent. There is,further, no method of programming the stent diameter along itslongitudinal axis to achieve a tapering stent design, and no method ofreenforcement of stent ends or other regions is provided for.

[0014] These and other conventional stent designs suffer in varyingdegrees from a variety of drawbacks including: (a) inability tonegotiate bends in vessels due to columnar rigidity of the unexpandedstent; (b) lack of structural strength, axio-lateral, of the unexpandedstent; (c) significant foreshortening of the stent during expansion; (d)limited stent length; (e) constant expanded stent diameter; (f) poorcrimping characteristics; and (g) rough surface modulation of theunexpanded stent.

[0015] There is a need for a stent with sufficient longitudinalflexibility in the unexpanded state to allow for navigation throughtortuous vessels. There is a further need for a stent that isstructurally strong in the unexpanded state such that risk of damage ordistortion during delivery is minimal. A further need exists for a stentthat maintains substantially the same longitudinal length duringexpansion to allow greater coverage at the target site and simplifyproper placement of the stent. Yet a further need exists for a stentdesign with sufficient longitudinal flexibility that long stents of upto 100 mm can be safely delivered through tortuous vessels. There is aneed for a stent that is configured to expand to variable diametersalong its length, such that a taper can be achieved in the expandedstent to match the natural taper of the target vessel. A need exists fora stent which, (i) can be crimped tightly on the expansion balloon whilemaintaining a low profile and flexibility, (ii) has a smooth surfacemodulation when crimped over a delivery balloon, to prevent catching andsnagging of the stent on the vessel wall during delivery or (iii) withreenforcement rings on the ends or middle or both to keep the ends ofthe stent securely positioned against the vessel walls of the targetblood vessel.

SUMMARY OF THE INVENTION

[0016] Accordingly an object of the present invention is to provide ascaffold for an interior lumen of a vessel.

[0017] Another object of the invention is to provide a stent whichprevents recoil of the vessel following angioplasty.

[0018] A further object of the invention is to provide a stent thatmaintains a larger vessel lumen compared to the results obtained onlywith balloon angioplasty.

[0019] Yet another object of the invention is to provide a stent thatreduces foreshortening of a stent length when expanded.

[0020] Another object of the invention is to provide a stent withincreased flexibility when delivered to a selected site in a vessel.

[0021] A further object of the invention is to provide a stent with alow profile when crimped over a delivery balloon of a stent assembly.

[0022] Yet a further object of the invention is to provide a stent withreduced tuliping of a stent frame.

[0023] Another object of the invention is to provide a chain mesh stentthat reduces vessel “hang up” in a tortuous vessel or a vessel withcurvature.

[0024] A further object of the invention is to provide a chain meshstent that increases radial and axio-lateral strength of the expandedstent.

[0025] These and other objects of the invention are achieved in a stentin a non-expanded state. A first expansion column includes of aplurality of first expansion column strut pairs. A first expansion strutpair includes a first expansion strut adjacent to a second expansionstrut and a first joining strut that couples the first and secondexpansion struts at a proximal end of the first expansion strut pair. Asecond expansion strut pair includes a third expansion strut adjacent tothe second expansion strut and a second joining strut that couples thesecond and third expansion struts at a distal end of the secondexpansion strut pair. A third expansion strut pair includes a fourthexpansion strut adjacent to the third expansion strut and a thirdjoining strut that couples the third and fourth expansion struts at aproximal end of the third expansion strut pair. A fourth expansion strutpair includes a fifth expansion strut adjacent to the fourth expansionstrut and a fourth joining strut that couples the fourth and fifthexpansion struts at a distal end of the fourth expansion strut pair.

[0026] A first expansion strut pair first corner is formed where thefirst joining strut is coupled to the first expansion strut, and a firstexpansion strut pair second corner is formed where the first joiningstrut is coupled to the second expansion strut. A second expansion strutpair first corner is formed where the second joining strut is coupled tothe second expansion strut, and a second expansion strut pair secondcorner is formed where the second joining strut is coupled to the thirdexpansion strut. A third expansion strut pair first corner is formedwhere the third joining strut is coupled to the third expansion strut,and a third expansion strut pair second corner is formed where the thirdjoining strut is coupled to the fourth expansion strut. A fourthexpansion strut pair first corner is formed where the fourth joiningstrut is coupled to the fourth expansion strut, and a fourth expansionstrut pair second corner is formed where the fourth joining strut iscoupled to the fifth expansion strut.

[0027] A second expansion column includes of a plurality of secondexpansion column strut pairs. A first expansion strut pair includes afirst expansion strut adjacent to a second expansion strut and a firstjoining strut that couples the first and second expansion struts at aproximal end of the first expansion strut pair. A second expansion strutpair includes a third expansion strut adjacent to the second expansionstrut and a second joining strut that couples the second and thirdexpansion struts at a distal end of the second expansion strut pair. Athird expansion strut pair includes a fourth expansion strut adjacent tothe third expansion strut and a third joining strut that couples thethird and fourth expansion struts at a proximal end of the thirdexpansion strut pair. A fourth expansion strut pair includes a fifthexpansion strut adjacent to the fourth expansion strut and a fourthjoining strut that couples the fourth and fifth expansion struts at adistal end of the fourth expansion strut pair.

[0028] A first expansion strut pair first corner is formed where thefirst joining strut is coupled to the first expansion strut, and a firstexpansion strut pair second corner is formed where the first joiningstrut is coupled to the second expansion strut. A second expansion strutpair first corner is formed where the second joining strut is coupled tothe second expansion strut, and a second expansion strut pair secondcorner is formed where the second joining strut is coupled to the thirdexpansion strut. A third expansion strut pair first corner is formedwhere the third joining strut is coupled to the third expansion strut,and a third expansion strut pair second corner is formed where the thirdjoining strut is coupled to the fourth expansion strut. A fourthexpansion strut pair first corner is formed where the fourth joiningstrut is coupled to the fourth expansion strut, and a fourth expansionstrut pair second corner is formed where the fourth joining strut iscoupled to the fifth expansion strut.

[0029] A first connecting strut column is formed of a plurality of firstconnecting struts, each connecting strut of the first connecting strutcolumn includes a connecting strut proximal section, a connecting strutdistal section and a connecting strut intermediate section. A firstconnecting strut proximal section is coupled to the first corner of thesecond expansion strut pair of the first expansion strut column, and afirst connecting strut distal section is coupled to the first joiningstrut of the first expansion strut pair of the second expansion strutcolumn intermediate the first expansion strut pair first corner and thefirst expansion strut pair second corner. A second connecting strutproximal section is coupled to the first corner of the fourth expansionstrut pair of the first expansion strut column, and a second connectingstrut distal section is coupled to the third joining strut of the thirdexpansion strut pair of the second expansion strut column intermediatethe third expansion strut pair first corner and the third expansionstrut pair second corner.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030]FIG. 1A is a side elevation view of the pre-expansion mode of anembodiment of the stent of the present invention;

[0031]FIG. 1B is a cross sectional view of an embodiment of the stent ofthe present invention;

[0032]FIG. 1C is a longitudinal cross sectional view of an embodiment ofthe stent of the present invention;

[0033]FIG. 2A is a scale drawing of the strut pattern of an embodimentof the stent of the present invention;

[0034]FIG. 2B is an expanded view of a section of the pattern of FIG.2A;

[0035]FIG. 3A is a schematic illustration of a pre-expansion mode of anembodiment of the stent of the present invention;

[0036]FIG. 3B is a schematic illustration of the post-expansion mode ofan embodiment of the stent of the present invention;

[0037]FIG. 4A is a scale drawing including dimensions of an embodimentof the stent of the present invention;

[0038]FIG. 4B is an enlarged section of the scale drawing of FIG. 4A;

[0039]FIG. 5 is a scale drawing of an embodiment of the stent of thepresent invention with a tapered diameter in its post-expansion mode;

[0040]FIG. 6A is a scale drawing of an embodiment of the stent of thepresent invention with reenforcement expansion columns;

[0041]FIG. 6B is a perspective view of the embodiment of FIG. 6A;

[0042]FIG. 7A is a scale drawing of an embodiment of the stent of thepresent invention including relief notches at strut joints to increaseflexibility of the joints;

[0043]FIG. 7B is an enlarged region of the embodiment of FIG. 7A;

[0044]FIG. 7C is an enlarged view of a single connecting strut joiningtwo expansion strut pairs in accordance with the embodiment of FIG. 7A;

[0045]FIG. 8A is a side elevation view of an embodiment of the stent ofthe present invention;

[0046]FIG. 8B is a side elevation view of an embodiment of the stent ofthe present invention, shown as if the stent struts and space therebetween were transparent;

[0047]FIG. 8C is a scale drawing of an embodiment of the stent of thepresent invention;

[0048]FIG. 8D is a variation of the embodiment of the stent of FIG. 8C;

[0049]FIG. 8E is a perspective view of the embodiment of FIG. 8D;

[0050]FIG. 8F is a drawing illustrating the post-expansion mode of thestent of the embodiment of FIG. 8D of the present invention;

[0051]FIG. 8G is an enlarged view of a single connecting strut joiningtwo expansion strut pairs in accordance with an embodiment of thepresent invention;

[0052]FIG. 9A is a side elevation view of an embodiment of the stent ofthe present invention;

[0053]FIG. 9B is a perspective view of the embodiment of FIG. 9A;

[0054]FIG. 9C is a scale drawing of the embodiment of FIG. 9A;

[0055]FIG. 9D is an enlarged region of the drawing of FIG. 9C;

[0056]FIG. 9E is a scale drawing of an embodiment of the stent of thepresent invention;

[0057]FIG. 9F is a scale drawing of an embodiment of the stent of thepresent invention;

[0058]FIG. 9G is an enlarged view of a single connecting strut joiningtwo expansion strut pairs in accordance with an embodiment of thepresent invention;

[0059]FIG. 10A is a drawing of an alternate geometry of connectingstruts and joining struts in accord with the present invention;

[0060]FIG. 10B is a drawing of an alternate geometry of connectingstruts and joining struts in accord with the present invention;

[0061]FIG. 10C is a drawing of an alternate geometry of connectingstruts and joining struts in accord with the present invention;

[0062]FIG. 10D is a drawing of an alternate geometry of connectingstruts and joining struts in accord with the present invention;

[0063]FIG. 10E is a drawing of an alternate geometry of connectingstruts and joining struts in accord with the present invention;.

[0064]FIG. 10F is a drawing of an alternate geometry of connectingstruts and joining struts in accord with the present invention; and

[0065]FIG. 11 is a delivery balloon catheter, illustrating a method ofdeliver of a stent in accord with the present invention.

DETAILED DESCRIPTION

[0066] A first embodiment of the present invention is shown in FIGS. 1A,1B, 1C, 2A and 2B. Referring to FIG. 1A, an elongate hollow tubularstent 10 in an unexpanded state is shown. A proximal end 12 and a distalend 14 define a longitudinal length 16 of stent 10. The longitudinallength 16 of the stent 10 can be as long as 100 mm or longer. A proximalopening 18 and a distal opening 20 connect to an inner lumen 22 of stent10. Stent 10 can be a single piece, without any seams or welding jointsor may include multiple pieces.

[0067] Stent 10 is constructed of two to fifty or more expansion columnsor rings 24 connected together by interspersed connecting strut columns26. The first column on the proximal end 12 and the last column on thedistal end 14 of stent 10 are expansion columns 24.

[0068] Expansion columns 24 are formed from a series of expansion struts28, and joining struts 30. Expansion struts 28 are thin elongate membersarranged so that they extend at least in part in the direction of thelongitudinal axis of stent 10. When an outward external force is appliedto stent 10 from the inside by an expansion balloon or other means,expansion struts 28 are reoriented such that they extend in a morecircumferential direction, i.e. along the surface of cylindrical stent10 and perpendicular to its longitudinal axis. Reorientation ofexpansion struts 28 causes stent 10 to have an expanded circumferenceand diameter. In FIG. 1A, expansion struts 28 of unexpanded stent 10 areseen to extend substantially parallel to the longitudinal axis of stent10.

[0069] Expansion struts 28 are joined together by joining struts 30 toform a plurality of expansion strut pairs 32. Expansion strut pairs havea closed end 34 and an open end 36. Additional joining struts 30 jointogether expansion struts 28 of adjacent expansion strut pairs 32, suchthat expansion struts 28 are joined alternately at their proximal anddistal ends to adjacent expansion struts 28 to form expansion columns24. Each expansion column 24 contains a plurality, typically eight totwenty, twenty to sixty, or larger of expansion struts 28. Expansioncolumns are preferably continuous unbroken ring structures extendingaround the circumference of the stent 10; however, broken structures inwhich individual struts or pieces of struts are removed from anotherwise continuous expansion column 24 can also be used.

[0070] Connecting struts 38 connect adjacent expansion columns 24forming a series of interspersed connecting strut columns 26 eachextending around the circumference of stent 10. Each connecting strut 38joins a pair of expansion struts 28 in an expansion column 24 to anadjacent pair of expansion struts 28 in an adjacent expansion column 24.For stent 10 of FIG. 1A, the ratio of expansion struts 28 in anexpansion column 24 to connecting struts 38 in a connecting strut column26 is two to one; however, this ratio in general can be to 1 where x isgreater or less than two. Furthermore, since the stent 10 of FIG. 1Abegins with an expansion column 24 on the proximal end 12 and ends withan expansion column 24 on the distal end 14, if there are n expansioncolumns 24 with m expansion struts 28 per column, there will be m−1connecting strut columns 26, and n(m−1)/2 connecting struts 38.

[0071] The reduced number of connecting struts 38 in each connectingstrut column 26, as compared to expansion struts 28 in each expansioncolumn 24, allows stent 10 to be longitudinally flexibility.Longitudinal flexibility can be further increased by using a narrowwidth connecting strut, providing additional flexibility and supplenessto the stent as it is navigated around turns in a natural blood vessel.

[0072] At least a portion of the open spaces between struts in stent 10form asymmetrical cell spaces 40. A cell space or geometric cell is anempty region on the surface of stent 10, completely surrounded by one ora combination of stent struts, including expansion struts 28, connectingstruts 38, or joining struts 30. Asymmetrical cell spaces 40 are cellspaces which have no geometrical symmetry i.e. no rotation, reflection,combination rotation and reflection or other symmetry. Asymmetrical cellspaces 40 have an asymmetrical geometric configuration.

[0073] Asymmetrical cell spaces 40 in FIG. 1A are surrounded by a firstexpansion strut pair 32 in a first expansion column 24, a firstconnecting strut 38, a second expansion strut pair 32 in an adjacentexpansion column 24, a first joining strut 30, a second connecting strut38, and a second joining strut 30. Furthermore, expansion strut pairs 32of asymmetrical cell space 40 may be circumferentially offset i.e. havelongitudinal axes that are not collinear and have their open ends 36facing each other. The space between two expansion struts of anexpansion strut pair 32 is known as a loop slot 42.

[0074]FIG. 1B shows inner lumen 22, radius 44 and stent wall 46 of stent10. Stent wall 46 consists of stent struts including expansion struts28, connecting struts 38 and joining struts 30.

[0075]FIG. 1C shows, proximal end 12, distal end 14, longitudinal length16, inner lumen 22, and stent wall 46 of stent 10. Inner lumen 22 issurrounded by stent wall 46 which forms the cylindrical surface of stent10.

[0076] Referring now to FIGS. 2A and 2B, joining struts 30 of stent 10are seen to extend at an angle to the expansion struts 28, forming anarrow angle 48 with one expansion strut 28 in an expansion strut pair32 and a wide angle 50 with the other expansion strut 28 of an expansionstrut pair 32. Narrow angle 48 is less than ninety degrees, while wideangle 50 is greater than ninety degrees. Joining struts 30 extend bothlongitudinally along the longitudinal axis of stent 10 andcircumferentially, along the surface of the stent 10 perpendicular toits longitudinal axis.

[0077] Expansion strut spacing 52 between adjacent expansion struts 28in a given expansion column 24 are uniform in stent 10 of FIGS. 2A and2B; however, non-uniform spacings can also be used. Expansion strutspacings 52 can be varied, for example, spacings 52 between adjacentexpansion struts 28 in an expansion column 24 can alternate between anarrow and a wide spacings. Additionally, spacings 52 in a singleexpansion column 24 can differ from other spacings 52 in other columns24.

[0078] It is noted that varying expansion strut spacings 52 which formthe loop slots 42 results in variable loop slot widths. Furthermore, thelongitudinal axis of the loop slots 42 need not be collinear or evenparallel with the longitudinal axis of loop slots 42 of an adjacentexpansion column 24. FIGS. 2A and 2B show an arrangement of expansionstruts 28 such that collinear, parallel adjacent loop slots 42 areformed, but non-collinear and non-parallel loop slots 42 can also beused.

[0079] Additionally the shape of loop slots 42 need not be the sameamong loop slots of a single or multiple expansion columns 24. The shapeof loop slots 42 can be altered by changing the orientation or physicaldimensions of the expansion struts 28 and/or joining struts 30 whichconnect expansion struts 28 of expansion strut pairs 32 defining theboundaries of loop slots 42.

[0080] Connecting struts 38 couple adjacent expansion columns 24, byconnecting the distal end of an expansion strut pair in one expansioncolumn 24 to the proximal end of an adjacent expansion strut pair 32 ina second expansion column 24. Connecting struts 38 of FIGS. 2A and 2Bare formed from two linear sections, a first linear section 54 beingjoined at its distal end to a second linear section 56 at its proximalend to form a first slant angle 58.

[0081] The first linear section 54 of a connecting strut 38 is joined toexpansion strut 28 at the point where joining strut 30 makes narrowangle 48 with expansion strut 28. First linear section 54 extendssubstantially collinear to joining strut 30 continuing the line ofjoining strut 30 into the space between expansion columns 24. The distalend of the first linear section 54 is joined to the proximal end of thesecond linear section 56 forming slant angle 58. Second linear section56 extends substantially parallel to expansion struts 28 connecting atits distal end to joining strut 30 in an adjacent expansion column 24.The distal end of second linear section 56 attaches to expansion strut28 at the point where joining strut 30 makes narrow angle 48 withexpansion strut 28. Further, joining strut 30 can have a second slantangle with a width that can be the same or different from the width ofthe first slant angle.

[0082]FIGS. 2A and 2B show connecting struts 38 and joining struts 30slanted relative to the longitudinal axis of stent 10, with thecircumferential direction of the slanted struts alternating from columnto adjacent column. Circumferential direction refers to the handednesswith which the slanted struts wind about the surface of the stent 10.The circumferential direction of the slant of connecting strut firstlinear sections 54 in a connecting strut column 26 is opposite thecircumferential direction of the slant of connecting strut first linearsections 54 in an adjacent connecting strut column 26. Similarly, thecircumferential direction of the slant of joining struts 30 in anexpansion column 24 is opposite the circumferential direction of theslant of joining struts 30 in an adjacent expansion column 24.Alternating circumferential slant directions of connecting struts 38 andjoining struts 30, prevents axial warping of stent 10 during deliver andexpansion. Other non-alternating slant direction patterns can also beused for connecting struts 38 or joining struts 30 or both.

[0083]FIG. 3A and 3B show a schematic illustration of a stent designaccording to the present invention in an unexpanded and expanded staterespectively. The design is depicted as a flat projection, as if stent10 were cut lengthwise parallel to its longitudinal axis and flattenedout. The connecting struts 38 consist of first and second linearsections 54 and 56 forming slant angle 58 at pivot point 60. Anasymmetrical cell space 40 is formed by expansion strut pairs 32,connecting struts 38 and joining struts 30. Multiple interlockingasymmetrical cell spaces 40 make up the design pattern.

[0084] As the stent is expanded, see FIG. 3B, the expansion strut pairs32 spread apart at their open ends 36, shortening the length ofexpansion struts 28 along the longitudinal axis of the cylindricalstent. The longitudinal shortening of expansion struts 28 duringexpansion is countered by the longitudinal lengthening of connectingstruts 38. The widening of slant angle 58 during expansion straightensconnecting struts 38 and lengthens the distance between the coupledexpansion strut pairs 32. The widening of the slant angle of connectingstruts 38 substantially compensates for the longitudinal shortening ofexpansion struts 28. Thus, the stent has substantially constantunexpanded and expanded longitudinal lengths.

[0085] When the stent is expanded, each expansion column 24 becomescircumferentially stretched, enlarging the space between struts. Theinterlinking of expansion columns 24 by connecting struts 38 that havebeen straightened through the expansion process gives the stent 10 ahigh radial support strength. The entire stent 10 when expanded isunitized into a continuous chain mesh of stretched expansion columns 24and connecting strut columns 26 forming an asymmetrical interlockingcell geometry which resists collapse both axially and radially. When thestent is expanded it has increased rigidity and fatigue tolerance.

[0086] In addition, efficient bending and straightening of connectingstruts 38 at pivot points 60 allows increased longitudinal flexibilityof the stent. For the stent to bend longitudinally, at least some ofconnecting struts 38 are forced to bend in their tangent plane. Thetangent plane of a specific connecting strut 38 refers to the planesubstantially tangent to the cylindrical surface of the stent at thatconnecting strut 38. The width of connecting struts 38 can be twice aswide as a thickness. Preferably, a one-to-one ratio is preferred.However, pivot points 60 in connecting struts 38 provide connectingstruts 38 a flexible joint about which to more easily bend increasinglongitudinal flexibility of the stent.

[0087] Referring to FIGS. 4A and 4B, a variation of the first embodimentof stent 10 of the present invention is shown. In this variation, stent10 has a length 16 of 33.25 mm and an uncrimped and unexpandedcircumference 88 of 5.26 mm. Fifteen expansion columns 24 areinterspersed with connecting strut columns 26. Each expansion column 24consists of twelve expansion struts 28 joined alternately at theirproximal and distal ends by joining struts 30 forming six expansionstrut pairs 32. Expansion struts 28 are aligned parallel to thelongitudinal axis of cylindrical stent 10. Joining struts 30 form anarrow angle 48 and a wide angle 50 with the respective expansion struts28 of expansion strut pairs 32. Adjacent expansion columns 24 employalternating circumferential slant directions of joining struts 30.

[0088] In this variation of the first embodiment, expansion strut width62 is 0.20 mm, expansion strut length 64 is 1.51 mm, and connectingstrut width 66 is 0.13 mm. Distance 68 from the outer edge of a firstexpansion strut 28 to the outer edge of a second adjacent expansionstrut 28 in the same expansion column 24 is 0.64 mm, leaving a loop slotwidth 70 of 0.24 mm.

[0089] In this variation of the first embodiment, connecting struts 38consist of a slanted first linear section 54 joined to a second linearsection 56 at a slant angle 58. First linear section 54 is slightlylonger than second linear section 56 and is attached at its proximal endto an expansion strut 28 in an expansion column 24. The attachment ofthe proximal end of first linear section 54 to expansion strut 28 is atthe point where joining strut 30 makes narrow angle 48 with expansionstrut 28. First linear section 54 extends substantially collinear tojoining strut 30 attaching at its distal end to the proximal end ofsecond linear section 56 to form slant angle 58. Second linear section56 extends substantially collinear to expansion struts 28, attaching atits distal end to an expansion strut 28 in an adjacent expansion column24. The attachment occurs at the point where expansion strut 28 formsnarrow angle 48 with joining strut 30. Joining struts 30 and connectingstrut first linear sections 54 slant in alternating circumferentialdirections from column to adjacent column.

[0090] The joining of connecting struts 38 and expansion struts 28 atthe point where narrow angle 48 is formed aids smooth delivery of stent10 by streamlining the surface of the unexpanded stent and minimizingpossible catching points. Bare delivery of stent 10 to the target lesionin a vessel will thus result in minimal snagging or catching as it isnavigated through turns and curvatures in the vessel. Stent 10 behaveslike a flexible, tubular sled as it is moved forward or backward in thevessel on the delivery catheter, sliding through tortuous vessels andover irregular bumps caused by atherosclerotic plaques inside the vessellumen.

[0091] When fully expanded Stent 10 of FIGS. 4A and 4B has an internaldiameter of up to 5.0 mm, while maintaining an acceptable radialstrength and fatigue tolerance. The crimped stent outer diameter can beas small as 1.0 mm or less depending on the condition of the underlyingdelivery balloon profile; A small crimped outer diameter is especiallyimportant if stent delivery is to be attempted without predilation ofthe target site. When the stent is optimally crimped over the deliveryballoon, the surface of the crimped stent is smooth allowing for nosnagging of the stent struts during either forward or backward movementthrough a vessel.

[0092]FIG. 5 shows a second embodiment of the present invention in whichthe stent 10 in its expanded form has a gradual taper from proximal end12 to distal end 14. The shaded segments 72, 74, 76, 78, 80, 82 and 84of expansion struts 28 represent regions of expansion struts 28 to beremoved. Removal of the shaded segments 72, 74, 76, 78, 80, 82 and 84provides stent 10 with a gradual taper when expanded with distal end 14having a smaller expanded diameter than proximal end 12. The degree ofshortening of the expanded diameter of the stent 10 at a given expansioncolumn 24 will be proportional to the length of the removed segment 72,74, 76, 78, 80, 82, or 84 at that expansion column 24. In the expandedstent 10 the shortened expansion struts 28 will have a shortenedcomponent along the circumference of the stent resulting in a shortenedcircumference and diameter. The tapered diameter portion can bepositioned anywhere along the length of stent 10, and the tapering canbe made more or less gradual by removing appropriately larger or smallerportions of the expansion struts 28 in a given expansion column 24.

[0093] Tapering is especially important in long stents, longer than 12mm, since tapering of blood vessels is more pronounced over longerlengths. A long stent with a uniform stent diameter can only be matchedto the target vessel diameter over a short region. If the proximalvessel size is matched with the stent diameter, the expanded distal endof the stent will be too large for the natural vessel and may cause anintimal dissection of the distal vessel by stent expansion. On the otherhand, if the distal vessel size is matched with the stent diameter, theproximal end of the expanded stent will be too small to set inside thevessel lumen. It is therefore desirable to have a stent with a taperedexpanded diameter.

[0094] Another way achieve a tapered expanded stent is to change thestiffness of the stent struts, expansion struts, connecting struts orjoining struts such that the stiffness of the struts varies along thelength of the stent. The stiffness of the struts can be changed byaltering length, width or thickness, adding additional stiffeningmaterial, using a chemical or mechanical means to alter the physicalproperties of the stent material, or applying one or a series of elasticelements about the stent.

[0095] Along with the use of a tapered diameter stent, a matchingtapered balloon catheter would ideally be made for delivery anddeployment of the tapered diameter stent. The method of using a taperedmatching balloon catheter with a tapered diameter stent is within thescope of the present invention.

[0096] Using a tapered balloon to expand a non-tapered stent will alsoachieve a tapered expanded stent; however, since no metal is removedfrom the stent, the stent is tapered as a result of incompleteexpansion. The stent will therefore have increased metal fraction at thetapered end resulting in increased risk of acute thrombosis. Metalfraction is the proportion of the surface of the expanded stent coveredby the stent strut material. Shortening the expansion struts as shown inFIG. 5 allows for a tapered expanded stent with substantially constantmetal fraction along its length.

[0097] A third embodiment of the present invention shown in FIGS. 6A and6B has multiple reenforcement expansion columns 86 placed along thelength of the stent 10. The Reenforcement columns 86 are placed alongthe stent length to provide additional localized radial strength andrigidity to stent 10. Additional strength and rigidity are especiallyimportant at the ends of the stent to prevent deformation of the stentboth during delivery and after placement. During delivery the stent endscan catch on the vessel wall possibly deforming the unexpanded stent andaltering its expansion characteristics. After the stent has been placedit is important that the stent ends are rigid so that they set firmlyagainst the vessel wall; otherwise, during a subsequent catheterprocedure, the catheter or guidewire can catch on the stent ends pullingthe stent away from the vessel wall and possibly damaging and/orblocking the vessel.

[0098] The specific variation of the third embodiment of stent 10depicted in FIGS. 6A and 6B has a length 16 of 20.70 mm and an uncrimpedand unexpanded circumference 88 of 5.26 mm. The stent 10 consists of sixexpansion columns 24 and three reenforcement expansion columns 86, eachconsisting respectively of twelve expansion struts 28 or reenforcementexpansion struts 90. The reenforcement expansion columns 86 arepositioned one at either end, and one along the length of the stent 10.

[0099] The expansion strut width 62 is 0.15 mm, reenforcement expansionstrut width 92 is 0.20 mm, and the connecting strut width 66 is 0.10 mm.The narrow angle 48 formed by joining strut 30 and expansion strut 28 is75 degrees, and the narrow angle 94 formed by reenforcement joiningstrut 96 and reenforcement expansion strut 90 is 60 degrees.

[0100] Other arrangements of reenforcement expansion columns 86, such asproviding reenforcement expansion columns 86 only on the ends of thestent, only on one end, or at multiple locations throughout the lengthof the stent can also be used and fall within the scope of the presentinvention. A taper can also be programmed into the reenforced stent 10by shortening expansion struts 28 and reenforcement expansion struts 90in appropriate expansion columns 24 and 86.

[0101] A fourth embodiment of the present invention, shown in the FIGS.7A, 7B and 7C, is similar to the third embodiment but has the addedfeature of relief notches 98 and 100. A relief notch is a notch wheremetal has been removed from a strut, usually at a joint where multiplestruts are connected. Relief notches increase flexibility of a strut orjoint by creating a thinned, narrow region along the strut or joint.Relief notch 98 is formed at the joint formed between first linearsection 54 of connecting strut 38 and expansion strut 28. Relief notch100 is formed at the joint between second linear section 56 ofconnecting strut 38 and expansion strut 28. The positioning of therelief notches gives added flexibility to the unexpanded stent andprevents warping at the joints when the stent is expanded. This resultsin a smooth surface modulation to the expanded stent frame. Reliefnotches can be placed at other joints and can be included in any of thepreviously mentioned embodiments.

[0102]FIGS. 8A and 8B show a side elevation view of a variation of thefifth embodiment of the stent of the present invention. In thisembodiment a four piece slanted connecting strut 38 is used to couplethe corner of an expansion strut pair 32 in one expansion column 24 tothe joining strut 30 of a circumferentially offset expansion strut pair32 in an adjacent expansion column 24. The expansion struts 28, joiningstruts 30, expansion columns 24, reenforcement expansion struts 90,reenforcement joining struts 96, and reenforcement expansion columns 86are substantially similar to the fourth embodiment of FIG. 6A.Connecting struts 38 in connecting strut columns 26, however, have analtered geometry and connectivity, described in more detail below.

[0103]FIG. 8A shows only the stent struts on the front half of the stentsurface. The stent struts on the rear half of the stent surface are notshown. The stent appears as it would if the stent struts and space therebetween were opaque. FIG. 8B shows all stent struts from both the frontand rear halves. The stent appears as it would if the stent struts andthe space there between were transparent.

[0104] A first variation of a fifth embodiment of the present invention,shown in FIG. 8C consists of a stent 10 with twelve expansion columns24, four reenforcement expansion columns 86, and fifteen connectingstrut columns 26. In this variation, the stent 10 has a length 16 of31.96 mm, and an unexpanded circumference 88 of 5.26 mm.

[0105] Connecting struts 38 shown in an enlarged view in FIG. 8G aremade up of four linear sections, a proximal end section 162, first andsecond intermediate sections 164 and 166 respectively and a distal endsection 168 forming three slant angles 170, 172 and 174. The proximalend of proximal section 162 is attached to a corner 176 of an expansionstrut pair 32 of an expansion column 24. Corner 176 is formed wherejoining strut 30 makes narrow angle 48 with expansion strut 28. A secondcorner 178 of expansion strut 32 is formed where joining strut 30 makeswide angle 50 with expansion strut 28. Corners 176 and 178 can have anangular shape formed by joining linear expansion struts 28 and joiningstruts 30, or preferably corners 176 and 178 are rounded to remove sharpedges and provide increased flexibility. Additionally rounded cornersprovide stent 10 with greater expandability and reduce stress in thestent strut material at the corners in the expanded stent.

[0106] Proximal end section 162 of connecting strut 38 extends fromcorner 176 and is attached at its distal end to first intermediatesection 164 forming slant angle 170. First intermediate section 164extends from proximal end section 162 such that first intermediatesection 164 is parallel to expansion struts 28 and is connected at itsdistal end to the proximal end of second intermediate section 166forming slant angle 172.

[0107] Second intermediate section 166 extends in a slanted orientationrelative to the longitudinal axis of stent 10, extending bothlongitudinally along and circumferentially about stent 10. Preferably,second intermediate section 166 is parallel to joining strut 30 of thecircumferentially offset expansion strut pair 32 in adjacent expansioncolumn 24.

[0108] Second intermediate section 166 attaches at its distal end to theproximal end of distal end section 168 forming slant angle 174. Distalend section 168 extends from second intermediate section 166 attachingat its distal end to joining strut 30 of circumferentially offsetexpansion strut pair 32 of adjacent expansion column 24. The attachmentis at a point intermediate corners 176 and 178, where joining strut 30forms narrow angle 48 and wide angle 50 respectively with expansionstruts 28.

[0109] The connection point of distal end section 168 to joining strut30 is closer to corner 176 than corner 178. Preferably the connectionpoint is one to two or more expansion strut widths from corner 176.Offsetting the connection point of distal end section 168 to joiningstrut 30 from corner 176 to a point intermediate corner 176 and corner178 reduces warping of the expanded stent 10, resulting in a smoothsurface modulation and reduced risk of thrombosis. Additionally, thisdesign provides a longer total straightened length of connecting strut38, which further reduces foreshortening of stent 10 during expansion.

[0110] A second variation of a fifth embodiment of the presentinvention, shown in an unexpanded form in FIGS. 8D, 8E and in anexpanded form in FIG. 8F consists of a stent 10 with six expansioncolumns 24, two reenforcement expansion columns 86, and seven connectingstrut columns 26. In this variation, the stent 10 has a length 16 of15.04 mm, and an unexpanded circumference 88 of 5.26 mm. The stentdesign 10 is substantially similar to the design of the first variationof the fifth embodiment of FIG. 8C with a reduced number of expansioncolumns, reenforcement expansion columns, and connecting strut columns.

[0111]FIG. 8F illustrates a portion of the expanded stent 10 of thesecond variation of the fifth embodiment. After expansion of stent 10 byballoon or other means, the expansion struts 28 are spread apartcircumferentially, increasing the separation at the open end 36 ofexpansion strut pairs 32 resulting in an increase in the circumferenceof the stent 10. The spreading of the expansion struts 28 causes alongitudinal shortening of the expansion columns 24, which iscompensated by a straightening of the connecting struts 38. During theexpansion process, the slant angles 170, 172 and 174 widen straighteningthe connection struts 38, and causing an increase in the separationdistance between adjacent expansion columns 24. The asymmetricalinterlocking cell geometry of the expanded stent is illustrated in FIG.8F.

[0112]FIGS. 9A, 9B, 9C, 9D, 9E, 9F and 9G illustrate a sixth embodimentof the stent of the present invention. In this embodiment a three pieceslanted connecting strut 38 is used to couple the joining strut 30 of anexpansion strut pair 32 in one expansion column 24 to the joining strut30 of a circumferentially offset expansion strut pair 32 in an adjacentexpansion column 24. The joints between segments of connecting strut 38are curved forming a smooth rounded shape. The expansion struts 28,joining struts 30, expansion columns 24, reenforcement expansion struts90, reenforcement joining struts 96, and reenforcement expansion columns86 are substantially similar to the fourth embodiment of FIG. 8A.Connecting struts 38 in connecting strut columns 26, however, have analtered geometry and connectivity, described in more detail below.

[0113] A first variation of a sixth embodiment of the present invention,shown in FIG. 9A, 9B and 9C consists of a stent 10 with eight expansioncolumns 24, three reenforcement expansion columns 86, and ten connectingstrut columns 26. In this variation, the stent 10 has a length 16 of20.32 mm.

[0114] Relief notches 204, are utilized at the joints betweenreenforcement expansion struts 90 and reenforcement joining struts 96 inthe reenforcement expansion columns 86 at the stent proximal end 12 anddistal end 14. Relief notches 204 reduce the width of the joints betweenreenforcement expansion struts 90 and reenforcement joining struts 96,which reduces stress in the metal at the joints during and afterexpansion of the stent. Relief notches 204 are particularly important atthe stent ends since the stent ends are especially susceptible towarping during and after expansion. Preferably relief notches 204 reducethe joint widths, such that the joint widths are substantially the sameas the thickness of stent wall 46 (see FIGS. 1B and 1C).

[0115] Connecting struts 38 shown in an enlarged view in FIG. 9D aremade up of three linear sections, a proximal end section 194, anintermediate section 196 and a distal end section 198 forming two slantangles 200, 202. The connecting struts 38 have wide radii of curvatureat the joints between connecting strut sections 194, 196 and 198. Theshape of connecting strut 38 is thus curved or wavy rather than jaggedand angular. The slant angles 200 and 202 are defined by linearlyextrapolating proximal end section 194, intermediate section 196 anddistal end section 198, as shown by the dotted lines in FIG. 9D.

[0116]FIG. 9E shows a variation of the connecting strut design of thesixth embodiment of the present invention. The connecting strut 38 ofFIG. 9E has smaller radii of curvature at the joints between proximalend section 194, intermediate section 196 and distal end section 198.Connecting strut 38 of FIG. 9E is thus more jagged and angular than thatof FIG. 9D.

[0117] Referring to the connecting struts 38 of FIG. 9D and 9E, theproximal end of proximal section 194 is attached to joining strut 30 ofexpansion strut pair 32 intermediate corners 176 and 178. Proximal endsection 194 of connecting strut 38 extends from joining strut 30 and isattached at its distal end to intermediate section 196 forming slantangle 200. Intermediate section 196 extends from proximal end section194 in a slanted orientation relative to the longitudinal axis of stent10, extending both longitudinally along and circumferentially aboutstent 10. Intermediate section 196 is preferably parallel to joiningstruts 30 of coupled expansion strut pairs 32.

[0118] Intermediate section 196 is connected at its distal end to theproximal end of distal end section 198 forming slant angle 202. Distalend section 198 extends from second intermediate section 196 attachingat its distal end to joining strut 30 of circumferentially offsetexpansion strut pair 32 of adjacent expansion column 24. The attachmentis at a point intermediate corners 176 and 178, where joining strut 30forms narrow angle 48 and wide angle 50 respectively with expansionstruts 28.

[0119] The connection point of proximal end section 194 and distal endsection 198 to joining struts 30 is closer to corner 176 than corner178. Preferably the connection point is one to two or more expansionstrut widths from corner 176. Offsetting the connection point of distalend section 198 to joining strut 30 from corner 176 to a pointintermediate corner 176 and corner 178 reduces warping of the expandedstent 10, resulting in a smooth surface modulation and reduced risk ofthrombosis. Additionally, this design provides a longer totalstraightened length of connecting strut 38, which further reducesforeshortening of stent 10 during expansion.

[0120] The connecting strut 38 of the sixth embodiment has one hundredand eighty degree rotational symmetry about its center. The symmetry ofthe connecting strut 38 does not, however, result in a symmetrical cellspace as the width of loop slots 42 connected in each cell space aredifferent. Adjacent loop slots 42 in each expansion column havealternating narrow and wide widths, preserving the asymmetry of the cellspaces. Introduction of one or many symmetrical cell spaces can beachieved in this design e.g. by providing uniform loop slot width toloop slots in adjacent expansion columns 24 contained in the same cellspace. Additionally completely non-uniform cell space patterns utilizingsymmetric or asymmetric cell spaces can be achieved e.g. by providingnon-uniform variations in the widths of loop slots 42.

[0121] A second variation of a sixth embodiment of the presentinvention, shown in an unexpanded form in FIG. 9F consists of a stent 10with six expansion columns 24, three reenforcement expansion columns 86,and eight connecting strut columns 26. In this variation, the stent 10has a length 16 of 16.00 mm, and an unexpanded circumference 88 of 5.26mm. The stent design 10 is substantially similar to the design of thefirst variation of the sixth embodiment of FIGS. 9A, 9B and 9C with areduced number of expansion columns 24 and connecting strut columns 26.

[0122] A third variation of a sixth embodiment of the present invention,shown in an unexpanded form in FIG. 9F consists of a stent 10 withtwelve expansion columns 24, four reenforcement expansion columns 86,and fifteen connecting strut columns 26. In this variation, the stent 10has a length 16 of 30.01 mm, and an unexpanded circumference 88 of 5.26mm. The stent design 10 is substantially similar to the design of thefirst variation of the sixth embodiment of FIGS. 9A, 9B and 9C with anincreased number of expansion columns 24 reenforcement expansion columns86 and connecting strut columns 26.

[0123]FIGS. 10A, 10B, 10C, 10D, 10E and 10F illustrate some examples ofalternate connecting strut designs which can be used in any of thepreviously discussed embodiments. FIG. 10A shows a rounded loopconnecting strut 38 which joins two circumferentially offset expansionstrut pairs 32 in adjacent expansion columns. Expansion struts 28 ineach expansion strut pair 32 are joined by a joining strut 30. Joiningstruts 30 are slanted such as to form a narrow angle 48 and a wide angle50 with the expansion struts 28 they connect. The rounded loopconnecting strut 38 connects expansion struts 28 at the point wherenarrow angle 48 is formed between expansion struts 28 and joining struts30. The slopes of the rounded connecting strut 38 at its proximal end102 and distal end 104 substantially match the slopes of the joiningstruts 30 connecting the pairs of expansion struts 28. The rounded loopconnecting strut 38 thus blends smoothly into the joining struts 30.Additionally the rounded loop connecting strut 38 has a first radius ofcurvature 106 and a second radius of curvature 108.

[0124] In the design of FIG. 10B a rounded loop connecting strut 38joins two circumferentially offset expansion strut pairs 32 in adjacentexpansion columns. Expansion struts 28 in each expansion strut pair 32are joined by a joining strut 30. Joining struts 30 are at right anglesto the expansion struts 28 they connect. The rounded loop connectingstrut 38 connects to expansion struts 28 at the same point as joiningstruts 30. The rounded connecting strut 38 has a first radius ofcurvature 106 and a second radius of curvature 108 such that it connectscircumferentially offset expansion strut pairs 32.

[0125] In the design of FIG. 10C connecting strut 38 joins twocircumferentially offset expansion strut pairs 32 in adjacent expansioncolumns. Expansion struts 28 in each expansion strut pair 32 are joinedby a joining strut 30. Joining struts 30 are slanted such as to form anarrow angle 48 and a wide angle 50 with the expansion struts 28 theyconnect. The connecting strut 38 connects expansion struts 28 at thepoint where narrow angle 48 is formed between expansion strut 28 andjoining strut 30.

[0126] The connecting strut 38 is made up of three linear sections 110,112, and 114 forming two slant angles 116 and 118. The proximal end ofsection 110 is attached to expansion strut 28 at the point where joiningstrut 30 forms narrow angle 48 with expansion strut 28. Section 110extends substantially collinear to joining strut 30 and is attached atits distal end to intermediate section 112 forming slant angle 116.Intermediate section 112 extends at an angle to section 110 such thatintermediate section 112 is substantially parallel to expansion struts28 and is connected at its distal end to the proximal end of distalsection 114 forming slant angle 118. Distal section 114 extends at anangle such that it is substantially collinear to joining strut 30 of theadjacent expansion strut pair 32. Distal section 114 attaches at itsdistal end to expansion strut 28 of the adjacent expansion strut pair32, at the point where joining strut 30 forms narrow angle 48 withexpansion strut 28.

[0127] In the design of FIGS. 10D and 10E a connecting strut 38 joinstwo circumferentially offset expansion strut pairs 32 in adjacentexpansion columns. Expansion struts 28 in each expansion strut pair 32are joined by a joining strut 30. Joining struts 30 are at right anglesto the expansion struts 28 they connect. The connecting strut 38connects to expansion struts 28 at the same point as joining struts 30.

[0128] The connecting struts 38 of FIGS. 10D and 10E are made up ofmultiple connecting strut sections connected end to end to form a jaggedconnecting strut 38 with multiple slant angles, coupling expansion strutpair 32 to adjacent expansion strut pair 32. The connecting strut ofFIG. 10D is made up of three connecting strut sections, a proximalsection 120, an intermediate section 122 and a distal section 124defining two slant angles 126 and 128, while the connecting strut ofFIG. 10E consists of four connecting strut sections, a proximal section130, intermediate sections 132 and 134, and a distal section 136defining three slant angles 138, 140 and 142. In addition, connectingstrut section 134 can be modified by replacing connecting strut section136 by the dotted connecting strut section 144 to give another possiblegeometry of connecting struts 38.

[0129] In the design of FIGS. 10F connecting strut 38 joins twocircumferentially offset expansion strut pairs 32 in adjacent expansioncolumns. Expansion struts 28 in each expansion strut pair 32 are joinedby a joining strut 30. Joining struts 30 are slanted such as to form anarrow angle 48 and a wide angle 50 with the expansion struts 28 theyconnect.

[0130] Connecting strut 38 is made up of four linear sections, aproximal end section 180, first and second intermediate sections 182 and184 respectively and a distal end section 186 forming three slant angles188, 190 and 192. The proximal end of section 180 is attached to corner176 at the point where joining strut 30 forms narrow angle 48 withexpansion strut 28. Proximal end section 180 extends at an angle tojoining strut 30 and is attached at its distal end to first intermediatesection 182 forming slant angle 188. First intermediate section 182extends at an angle to proximal end section 180 such that firstintermediate section 182 is substantially parallel to expansion struts28 and is connected at its distal end to the proximal end of secondintermediate section 184 forming slant angle 190. Second intermediatesection 184 is substantially longer than the first intermediate section182. Second intermediate section 184 extends at an angle such that it issubstantially collinear to joining strut 30 of the adjacent expansionstrut pair 32. Second intermediate section 184 attaches at its distalend to the proximal end of distal end section 186 forming slant angle192. Distal end section 186 extends in a slightly sloping orientationrelative to expansion struts 28, attaching to corner 176 of expansionstrut pair 32 where joining strut 30 forms narrow angle 48 withexpansion strut 28. Relief notches 206 are formed at the joint betweendistal end segment 186 of connecting strut 38 and corner 176 ofexpansion strut pair 32 to increase flexibility of the unexpended stentand prevent warping when the stent is expanded.

[0131] One skilled in the art will recognize that there are manypossible arrangements of connecting struts and joining struts consistentwith the present invention; the above examples are not intended to be anexhaustive list. In particular, it is noted that (a) connecting strutsections need not be linear but may contain one or many radii ofcurvature, (b) connecting strut sections may each have a differentlongitudinal axis, (c) the joint between connecting strut sections neednot be jagged or sharp, but rather can be smooth containing one ormultiple radii of curvature, and (d) relief notches may be present atany of the strut joints.

[0132] The stent of the present invention is ideally suited forapplication in coronary vessels although versatility in the stent designallows for applications in non-coronary vessels, the aorta, andnonvascular tubular body organs.

[0133] Typical coronary vascular stents have expanded diameters thatrange from 2.5 to 5.0 mm. However, a stent with high radial strength andfatigue tolerance that expands to a 5.0 mm diameter may haveunacceptably high stent metal fraction when used in smaller diametervessels. If the stent metal fraction is high, the chances of acutethrombosis and restenosis potential will increase. Even with the samemetal fraction a smaller caliber vessel is more likely than a larger oneto have a high rate of thrombosis. It is, therefore, preferred to haveat least two different categories of stents for coronary application,for example, small vessels stents for use in vessels with diameters from2.5 mm to 3.0 mm, and large vessel stents for use in vessels withdiameters from 3.0 mm to 5.0 mm. Thus, both small vessels and largevessels when treated with the appropriate sized stent will containstents of similar idealized metal fraction.

[0134] The stent of the present invention can be made using a CAM-drivenlaser cutting system to cut the stent pattern from a stainless steeltube. The rough-cut stent is preferably electro-polished to removesurface imperfections and sharp edges. Other methods of fabricating thestent can also be used such as EDM, photo-electric etching technology,or other methods. Any suitable material can be used for the stentincluding other metals and polymers so long as they provide theessential structural strength, flexibility, biocompatibility andexpandability.

[0135] The stent is typically at least partially plated with aradiopaque metal, such as gold, platinum, tantalum or other suitablemetal. It is preferred to plate only both ends of the stent by localizedplating; however, the entire stent or other regions can also be plated.When plating both ends, one to three or more expansion columns on eachend of the stent are plated to mark the ends of the stent so they can beidentified under fluoroscopy during the stenting procedure. By platingthe stent only at the ends, interference of the radiopaque platingmaterial with performance characteristics or surface modulation of thestent frame is minimized. Additionally the amount of plating materialrequired is reduced, lowering the material cost of the stent.

[0136] After plating, the stent is cleaned, typically with detergent,saline and ultrasonic means that are well-known in the art. The stentsare then inspected for quality control, assembled with the deliveryballoon catheter, and properly packaged, labeled, and sterilized.

[0137] Stent 10 can be marketed as stand alone or as a pre-mounteddelivery balloon catheter assembly as shown in FIG. 1. Referring to FIG.11, the stent 10 is crimped over a folded balloon 146 at the distal end148 of a delivery balloon catheter assembly 150. The assembly 150includes a proximal end adapter 152, a catheter shaft 154, a balloonchannel 156, a guidewire channel 158, a balloon 146, and a guidewire160. Balloon 146 can be tapered, curved, or both tapered and curved froma proximal end to a distal end in the expanded state. Additionally stent10 can be non-tapered or tapered in the expanded state.

[0138] Typically the guidewire 160 is inserted into the vein or arteryand advanced to the target site. The catheter shaft 154 is thenforwarded over the guidewire 160 to position the stent 10 and balloon146 into position at the target site. Once in position the balloon 146is inflated through the balloon channel 156 to expand the stent 10 froma crimped to an expanded state. In the expanded state, the stent 10provides the desired scaffolding support to the vessel. Once the stent10 has been expanded, the balloon 146 is deflated and the catheter shaft154, balloon 146, and guidewire 160 are withdrawn from the patient.

[0139] The stent of the present invention can be made as short as lessthan 10 mm in length or as long as 100 mm or more. If long stents are tobe used, however, matching length or preferably slightly longer deliverycatheter balloons will typically be needed to expand the stents intotheir deployed positions. Long stents, depending on the target vessel,may require curved long balloons, tapered long balloons or curved andtapered long balloons for deployment. Curved and/or tapered balloonswhich match the natural curve and taper of a blood vessel reduce stresson the blood vessel during and after stent deployment. This isespecially important in many coronary applications which involvestenting in curved and tapered coronary vessels. The use of such curvedand/or tapered balloons is within the scope of the present invention.

[0140] The foregoing description of a preferred embodiment of theinvention has been presented for purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Obviously, many modificationsand variations will be apparent to practitioners skilled in this art. Itis intended that the scope of the invention be defined by the followingclaims and their equivalents.

What is claimed is:
 1. A stent in a non-expanded state, comprising: afirst expansion column formed of a plurality of first expansion columnstrut pairs, a first expansion strut pair including a first expansionstrut adjacent to a second expansion strut and a first joining strutthat couples the first and second expansion struts at a proximal end ofthe first expansion strut pair, a second expansion strut pair includinga third expansion strut adjacent to the second expansion strut and asecond joining strut that couples the second and third expansion strutsat a distal end of the second expansion strut pair, a third expansionstrut pair including a fourth expansion strut adjacent to the thirdexpansion strut and a third joining strut that couples the third andfourth expansion struts at a proximal end of the third expansion strutpair, a fourth expansion strut pair including a fifth expansion strutadjacent to the fourth expansion strut and a fourth joining strut thatcouples the fourth and fifth expansion struts at a distal end of thefourth expansion strut pair, a first expansion strut pair first cornerformed where the first joining strut is coupled to the first expansionstrut, and a first expansion strut pair second corner formed where thefirst joining strut is coupled to the second expansion strut, and asecond expansion strut pair first corner formed where the second joiningstrut is coupled to the second expansion strut, and a second expansionstrut pair second corner formed where the second joining strut iscoupled to the third expansion strut, and a third expansion strut pairfirst corner formed where the third joining strut is coupled to thethird expansion strut, and a third expansion strut pair second cornerformed where the third joining strut is coupled to the fourth expansionstrut, and a fourth expansion strut pair first corner formed where thefourth joining strut is coupled to the fourth expansion strut, and afourth expansion strut pair second corner formed where the fourthjoining strut is coupled to the fifth expansion strut; a secondexpansion column formed of a plurality of second expansion column strutpairs, a first expansion strut pair including a first expansion strutadjacent to a second expansion strut and a first joining strut thatcouples the first and second expansion struts at a proximal end of thefirst expansion strut pair, a second expansion strut pair including athird expansion strut adjacent to the second expansion strut and asecond joining strut that couples the second and third expansion strutsat a distal end of the second expansion strut pair, a third expansionstrut pair including a fourth expansion strut adjacent to the thirdexpansion strut and a third joining strut that couples the third andfourth expansion struts at a proximal end of the third expansion strutpair, a fourth expansion strut pair including a fifth expansion strutadjacent to the fourth expansion strut and a fourth joining strut thatcouples the fourth and fifth expansion struts at a distal end of thefourth expansion strut pair, a first expansion strut pair first cornerformed where the first joining strut is coupled to the first expansionstrut, and a first expansion strut pair second corner formed where thefirst joining strut is coupled to the second expansion strut, and asecond expansion strut pair first corner formed where the second joiningstrut is coupled to the second expansion strut, and a second expansionstrut pair second corner formed where the second joining strut iscoupled to the third expansion strut, and a third expansion strut pairfirst corner formed where the third joining strut is coupled to thethird expansion strut, and a third expansion strut pair second cornerformed where the third joining strut is coupled to the fourth expansionstrut, and a fourth expansion strut pair first corner formed where thefourth joining strut is coupled to the fourth expansion strut, and afourth expansion strut pair second corner formed where the fourthjoining strut is coupled to the fifth expansion strut; and a firstconnecting strut column formed of a plurality of first connectingstruts, each connecting strut of the first connecting strut columnincluding a connecting strut proximal section, a connecting strut distalsection and a connecting strut intermediate section, a first connectingstrut proximal section is coupled to the first corner of the secondexpansion strut pair of the first expansion strut column, and a firstconnecting strut distal section is coupled to the first joining strut ofthe first expansion strut pair of the second expansion strut columnintermediate the first expansion strut pair first corner and the firstexpansion strut pair second corner, and a second connecting strutproximal section is coupled to the first corner of the fourth expansionstrut pair of the first expansion strut column, and a second connectingstrut distal section is coupled to the third joining strut of the thirdexpansion strut pair of the second expansion strut column intermediatethe third expansion strut pair first corner and the third expansionstrut pair second corner.
 2. The stent of claim 1, wherein eachconnecting strut proximal section has a substantially linear geometry.3. The stent of claim 2, wherein each connecting strut distal sectionhas a substantially linear geometry.
 4. The stent of claim 3, whereineach connecting strut intermediate section has a substantially lineargeometry.
 5. The stent of claim 3, wherein each connecting strutintermediate section includes a first linear section and a second linearsection.
 6. The stent of claim 5, wherein the first linear section ofthe first connecting strut intermediate section is shorter than thesecond linear section of the first connecting strut intermediatesection.
 7. The stent of claim 5, wherein each of a connecting strutproximal section, distal section, first linear section of theintermediate section and second linear section of the intermediatesection have a different longitudinal axis.
 8. The stent of claim 5,wherein a first slant angle is formed between the first linear sectionof the first connecting strut intermediate section and the second linearsection of the first connecting strut intermediate section.
 9. The stentof claim 5, further including a radius of curvature formed at the firstslant angle.
 10. The stent of claim 5, wherein a radius of curvature isformed between the first linear section and the second linear section ofthe first connecting strut intermediate section.
 11. The stent of claim5, wherein a second slant angle is formed between the second linearsection of the first connecting strut intermediate section and thedistal section of the first connecting strut.
 12. The stent of claim 5,wherein a radius of curvature is formed between the second linearsection of the first connecting strut intermediate section and thedistal section of the first connecting strut.
 13. The stent of claim 5,wherein a third slant angle is formed between the proximal section ofthe first connecting strut and the first linear section of the firstconnecting strut intermediate section.
 14. The stent of claim 5, whereina radius of curvature is formed between the proximal section of eachconnecting strut and the first linear section of each connecting strutintermediate section.
 15. The stent of claim 1, wherein a ratio of anumber of expansion struts in an expansion strut column to a number ofconnecting struts in a connecting strut column is 2 to
 1. 16. The stentof claim 1, wherein the stent includes m first and second expansioncolumns, n connecting struts per column and n (m−1)/2 connecting struts.17. The stent of claim 1, wherein the first and second expansion columnsare each unbroken, continuous column structures.
 18. The stent of claim1, wherein one of the first or second expansion column is a brokencolumn structure.
 19. The stent of claim 1, further comprising: aplurality of first expansion columns; a plurality of second expansioncolumns; and a plurality of first connecting strut columns, each firstconnecting strut column coupling a first expansion column to a secondexpansion column.
 20. The stent of claim 19, wherein the plurality offirst expansion columns, the plurality of second expansion columns andthe plurality of first connecting strut columns form an elongatedstructure.
 21. The stent of claim 1, wherein the first expansion column,the second expansion column, and the first connecting strut column forma plurality of geometric cells and at least a portion of the pluralityare symmetrical geometric cells.
 22. The stent of claim 1, wherein thefirst expansion column, the second expansion column, and the firstconnecting strut column form non-uniform cell space patterns.
 23. Thestent of claim 1, wherein the first expansion strut column, the secondexpansion strut column and the first connecting strut column formasymmetrical geometric configurations.
 24. The stent of claim 1, furthercomprising: a reenforcement expansion column made of a plurality ofreenforcement expansion struts, wherein each reenforcement expansionstrut has a width that is greater than a width of an expansion strut inthe first or second expansion, columns.
 25. The stent of claim 1,wherein the stent has a proximal end with a first reenforcementexpansion column and a distal end with a second reenforcement expansioncolumn.
 26. The stent of claim 1, wherein the stent has a reenforcementexpansion column between a proximal end and a distal end of the stent.27. The stent of claim 1, further comprising: a third expansion columnformed of a plurality of third expansion column strut pairs, a firstexpansion strut pair including a first expansion strut adjacent to asecond expansion strut and a first joining strut that couples the firstand second expansion struts at a proximal end of the first expansionstrut pair, a second expansion strut pair including a third expansionstrut adjacent to the second expansion strut and a second joining strutthat couples the second and third expansion struts at a distal end ofthe second expansion strut pair, a third expansion strut pair includinga fourth expansion strut adjacent to the third expansion strut and athird joining strut that couples the third and fourth expansion strutsat a proximal end of the third expansion strut pair, a fourth expansionstrut pair including a fifth expansion strut adjacent to the fourthexpansion strut and a fourth joining strut that couples the fourth andfifth expansion struts at a distal end of the fourth expansion strutpair, a first expansion strut pair first corner formed where the firstjoining strut is coupled to the first expansion strut, and a firstexpansion strut pair second corner formed where the first joining strutis coupled to the second expansion strut, and a second expansion strutpair first corner formed where the second joining strut is coupled tothe second expansion strut, and a second expansion strut pair secondcorner formed where the second joining strut is coupled to the thirdexpansion strut, and a third expansion strut pair first corner formedwhere the third joining strut is coupled to the third expansion strut,and a third expansion strut pair second corner formed where the thirdjoining strut is coupled to the fourth expansion strut, and a fourthexpansion strut pair first corner formed where the fourth joining strutis coupled to the fourth expansion strut, and a fourth expansion strutpair second corner formed where the fourth joining strut is coupled tothe fifth expansion strut; and a second connecting strut column formedof a plurality of second connecting struts, each connecting strut of thesecond connecting strut column including a connecting strut proximalsection, a connecting strut distal section and a connecting strutintermediate section, a first connecting strut proximal section iscoupled to the second corner of the second expansion strut pair of thesecond expansion strut column, and a first connecting strut distalsection is coupled to the first joining strut of the first expansionstrut pair of the third expansion strut column intermediate the firstexpansion strut pair first corner and the first expansion strut pairsecond corner, and a second connecting strut proximal section is coupledto the second corner of the fourth expansion strut pair of the secondexpansion strut column, and a second connecting strut distal section iscoupled to the third joining strut of the third expansion strut pair ofthe third expansion strut column intermediate the third expansion strutpair first corner and the third expansion strut pair second corner. 28.The stent of claim 1, wherein a width of the first connecting strut isequal to or less than a width of the first expansion strut of the firstor second expansion columns.
 29. The stent of claim 1, wherein a widthof a connecting strut of the first connecting strut column is largerthan a width of a first expansion strut of the first or second expansioncolumns.
 30. The stent of claim 1, wherein a width of the secondexpansion strut of the first or second expansion columns issubstantially the same as the width of the first expansion strut of thefirst or second expansion columns.
 31. The stent of claim 1, wherein aspace between the first and second expansion struts of the firstexpansion column is equal to a space between the second and thirdexpansion struts of the first expansion column.
 32. The stent of claim1, wherein a space between the first and second expansion struts of thefirst expansion column is less than a space between the second and thirdexpansion struts of the first expansion column.
 33. The stent of claim1, wherein a space between the first and second expansion struts of thefirst expansion column is larger than a space between the second andthird expansion struts of the first expansion column.